購物車功能在Python

Question

我目前Python中的任務，我需要這方面的幫助，我到

創建一個名爲ShoppingCart類。

創建一個沒有參數並將total屬性設置爲零的構造函數，並初始化一個名爲items的空dict屬性。

創建一個方法add_item，它需要item_name，quantity和price參數。此方法應將添加項目的成本添加到當前總值中。它還應該添加一個項目字典的條目，這樣的關鍵是item_name和值是項目的數量。

創建一個方法remove_item，它需要與add_item類似的參數。它應該刪除已添加到購物車並且不需要的商品。這種方法應該從當前總額中扣除這些項目的成本，並相應地更新項目字典。如果要移除的物品數量超過購物車中的當前數量，則假定該物品的所有條目都將被移除。

創建一個方法checkout，它接受cash_paid並從付款中返回餘額值。如果cash_paid不足以支付總額，則返還現金支付不足。

創建具有在100

初始化名爲量的屬性，確保從店繼承的購物構造一類叫做店。

在Shop類中，重寫remove_item方法，例如調用Shop的remove_item（不帶參數）數量減一。

下面是本

import unittest; 

class Test(unittest.TestCase): 
def setUp(self): 
    self.cart = ShoppingCart() 
    self.shop = Shop() 

def test_cart_property_initialization(self): 
    self.assertEqual(self.cart.total, 0, msg='Initial value of total not correct') 
    self.assertIsInstance(self.cart.items, dict, msg='Items is not a dictionary') 

def test_add_item(self): 
    self.cart.add_item('Mango', 3, 10) 
    self.assertEqual(self.cart.total, 30, msg='Cart total not correct after adding items') 
    self.assertEqual(self.cart.items['Mango'], 3, msg='Quantity of items not correct after adding item') 

def test_add_item_hidden(self): 
    self.cart.add_item('Mango', 3, 10) 
    self.cart.add_item('Orange', 16, 10) 
    self.assertEqual(self.cart.total, 190, msg='Cart total not correct after adding items') 
    self.assertEqual(self.cart.items['Orange'], 16, msg='Quantity of items not correct after adding item') 

def test_remove_item(self): 
    self.cart.add_item('Mango', 3, 10) 
    self.cart.remove_item('Mango', 2, 10) 
    self.assertEqual(self.cart.total, 10, msg='Cart total not correct after removing item') 
    self.assertEqual(self.cart.items['Mango'], 1, msg='Quantity of items not correct after removing item') 

def test_remove_item_hidden(self): 
    self.cart.add_item('Mango', 3, 10) 
    self.cart.add_item('Orange', 16, 10) 
    self.cart.remove_item('Mango', 2, 10) 
    self.assertEqual(self.cart.total, 170, msg='Cart total not correct after removing item') 
    self.assertEqual(self.cart.items['Mango'], 1, msg='Quantity of items not correct after removing item') 
    self.cart.remove_item('Mango', 2, 10) 
    self.assertEqual(self.cart.total, 160, msg='Cart total not correct after removing item') 
    with self.assertRaises(KeyError): 
     self.cart.items['Mango'] 

def test_checkout_returns_correct_value(self): 
    self.cart.add_item('Mango', 3, 10) 
    self.cart.add_item('Orange', 16, 10) 
    self.assertEqual(self.cart.checkout(265), 75, msg='Balance of checkout not correct') 
    self.assertEqual(self.cart.checkout(25), 'Cash paid not enough', msg='Balance of checkout not correct') 


def test_shop_is_instance_of_shopping_cart(self): 
    self.assertTrue(isinstance(self.shop, ShoppingCart), msg='Shop is not a subclass of ShoppingCart') 

def test_shop_initializaton(self): 
    self.assertEqual(self.shop.quantity, 100, msg='Shop quantity not initialized correctly') 

def test_shop_remove_item_method(self): 
    for i in range(15): 
     self.shop.remove_item() 

    self.assertEqual(self.shop.quantity, 85) 

樣品測試代碼我試圖與下面

class ShoppingCart(object): 

    def __init__(self): 
     self.total = 0 
     self.items = {} 

    def add_item(self,item_name,quantity,price): 
     self.items[item_name] = quantity 
     self.total += price*quantity 

    def remove_item(self,item_name,quantity,price): 
     if quantity < self.items[item_name] and quantity >= 0: 
      self.total -= price*quantity 
      self.items[item_name] -= quantity 
     elif quantity >= self.items[item_name] : 
      del self.items[item_name] 

    def checkout(self,cash_paid): 
     if cash_paid >= self.total: 
      return cash_paid - self.total 
     else: 
      return "Cash paid not enough" 

class Shop(ShoppingCart): 
    def __init__(self): 
     self.quantity = 100 

    def remove_item(self): 
     self.quantity -= 1 

代碼的所有其他任務都解決了，但錯誤我回來的回報的時候解決這個我運行測試是

test_remove_item_hidden 
170 != 160 : Cart total not correct after removing item 

我似乎無法找到問題。請任何幫助將考慮我是新來的蟒蛇。提前致謝。

Answer 1

刪除時，其他情況下調用del只刪除該項目，但不更新購物車總額。您應該使用該數量來降低總價格：

... 
else: 
    self.total -= price*self.items[item_name] 
    del self.items[item_name] 
...